1. Field of the Invention
The present invention relates to a tie bar made of resin, which is used to prevent softened molding resin from leaking out between leads of a lead frame during resin molding in producing a resin-molded semiconductor device; a tape for forming such a resin tie bar; a lead frame having a resin tie bar; a resin-molded semiconductor device that makes use of a resin tie bar; and a method for producing this device.
2. Description of the Related Art
When a resin-molded semiconductor device is produced, a lead frame on which a semiconductor chip has been mounted and which has been wire bonded is molded with a resin. In this resin molding step, the lead frame is clamped between upper and lower molds, and the cavity of the mold is filled with a heated and softened molding resin.
When this resin molding is performed, a tie bar is provided between the leads of the lead frame in order to prevent the molding resin, which is fluid, from leaking out from between the leads of the lead frame. This tie bar is usually formed integrally with the leads when the lead frame is etched, and is therefore composed of the same material as the lead frame, namely, an electroconductive metal.
Because the leads of a semiconductor device need to be insulated from one another, the tie bar is cut away after resin molding. However, as the pin count has risen in recent years, such as in a QFP (Quad Flat Package), the tendency has been for the lead pitch to narrow, and it is difficult to cut tie bars precisely between leads of such narrow pitch.
The use of tie bars made of resin instead of metal has been proposed in an effort to obviate the need for cutting away the tie bars (such as in Japanese Laid-Open Patent Applications H6-37126, H6-310652, and H7-161916, and Japanese Patent 3,047,716), but the accurate positioning of the tie bars was difficult in the formation of the tie bars on the lead frame, or the tie bars were not formed in the proper shape, leading to the risk of molding resin leakage from between the leads.